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Having trouble with Flir Vue Pro R and temperature calculation

Hi,

I am a very new Pix4D user (I am testing Pix4D), and  I’m trying to process thermal images from a Flir Vue Pro R 640, 19mm. Al the process run without problems. The problem appears  when we want to have and temperature related index.

I am applying the formula grayscale*0.04-273.15 to get temperature in ºC from the 14bit TIFF images, but the values I am obtaining are not reasonable. I am attaching an screen capture to show the values and parameters I am using.

What is wrong with my index calculation?

Thanks in advance.

Best regards!

Santiago

Hi,

When using the grayscale, the formula on the website does not work in all cases, as the way FLIR is saving the .TIFF images can vary depending on the camera and the version of it. At the moment we do not have all formulas that FLIR uses to create their .TIFF images. 

But since you have a radiometric version of your camera then you should use the radiometric jpegs (r-jpeg) for processing and not the grayscale. This would ensure the absolute values of the temperature.

Cheers,

Ina 

Dear Ina

 

Thank you very much for the reply.When i choose my camera type is it that the relevant formula is then applied in the grayscale segment and thereafter the reflectance map is generated.

 

Thank you

When a thermal project if created by default you will have 2 indices in the database 0.04*thermal_ir - 273.15 or therma_ir. Depending on the type of camera that you have then these indices formulas can be used to extract the temperature based on the irradiance map (aka reflectance map). 

Camera  Image format Formula to retrieve temperature
The radiometric version of the camera ®    r-jpeg no formula is needed; by extracting the indices from the band, you obtain the absolute temperature
   tiff 0.04*thermal_ir - 273.15, to obtain absolute temperature in Celsius (the formula is not expected to work in all the cases) 
The non-radiometric version of the camera    tiff no formula is needed, by retrieving the indices from the band you obtain the relative temperature with no units

Thermomap

|

   tiff

|

0.01*thermal_ir - 100

|

For the full workflow, please see: https://support.pix4d.com/hc/en-us/articles/360000173463-Processing-thermal-images#label5

Cheers,

Ina